Quantum Hall induced currents and the magnetoresistance of a quantum point contact

Abstract

We report measurements of quantum Hall induced currents from their magnetisation and from their effect on the conductance of a quantum point contact. Features in the magnetic moment and QPC resistance are correlated at Landau level filling factors \nu=1,2 and 4, demonstrating the common origin of the effects. Similar temperature and non-linear sweep rate dependences are observed for the two types of measurement, furthermore, `noisy' structures are observed in the induced currents with clear correlations in the two measurements. In contrast there is a distinct difference in the way in which the induced currents decay with time when the sweeping field is halted at integer filling factor. Although the effects of induced currents on the electrostatics of a QPC are clearly demonstrated we were unable to demonstrate the reverse effect: to influence the IC by altering the electrostatics of the QPC.